The present invention relates to systems and methods for various digital phased array and beamforming architectures that have a reduced need for digital bandwidth while maintaining the probability of detection and probability of false alarm of a traditional digital beamforming phased array.
Actively scanned phased arrays can use a multitude of antenna elements and phase shifting mechanisms to change the inbound signal phase, along with a summing network, to electronically form or scan a receive beam or set of beams for the overall phased array. This is often done within the analog domain with discrete phase shifter components, waveguides, and power combination circuits. Output of this analog beam former can be digitized and sent to a signal processor for signal detection. To form multiple receive beams, complete sets of phase shifters and waveguides are often necessary for each additional beam, adding to cost and weight.
Digital phased arrays can be designed to address such limitations where digitization occurs at an output of each subarray or even each antenna element receiver in the system. Samples from each digital channel can be weighted by a multiplier to adjust phase and amplitude and are then summed together, forming a digital receive beam signal defined by these weights and the distribution of antenna elements on the array. Multiple digital receive beams are formed by generating separate streams for each set of weights for each desired beam. Signal detection is done at the final summation point for these beams, depending on the application of the system. For radar systems, one goal can be to detect echo return pulses sent out earlier. Such detection can be done digitally by applying a matched filter to each receive beam and then running the resulting signal through a threshold detector, where crossings at particular time samples correspond to targets at a certain range or false detections due to noise.
Digital beamforming arrays must transport digitized sample data to other locations for summing and forming final receive beams. This is accomplished by a number of different architectures. A central summer can take in all samples from every stream and form any number of digital beams, limited only by the amount of processing power available. For very large arrays, a processor of this nature would require an enormous amount of digital input bandwidth and input connections.
A hierarchical beam former takes a layered approach by summing beam data from each digital channel at multiple tiers, reducing the amount of data into the final central processor. Hierarchical and other networked digital beamforming architectures are very dependent on the amount of digital bandwidth available between summation nodes and this digital bandwidth limits the total beam-bandwidth product. Various systems can either produce a large number of beams each with smaller sample rate, or a small number of beams each with a large sample rate.
Processing at each node is available in these architectures that can be adapted to add additional computational power than adding excess digital input/output (I/O) bandwidth. By pulling some of the signal detection processing that occurs at the final processor in a pulse-detecting system into each node for pre-processing, an amount of digital sample data that must be sent to the final processor can be greatly reduced. Embodiments of the invention can include an exemplary capability that can expand the amount of achievable beam-bandwidth for a fixed amount of digital I/O available between hierarchical beamforming nodes or would reduce the needed digital I/O capacity of a digital phased array. Embodiments of the invention can include an architecture that provide an ability for implementing signal predetection in digital phased arrays with distributed signal processing, and by using a hybrid detection methodology that combines binary integration and standard coherent processing at final beamforming nodes, digital I/O capacity needs are reduced while maintaining detection sensitivity of a standard coherent phased array architecture.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.